Snap-action device



Feb. 16, 1954 C, BRADLEY 2,669,618

SNAP-ACTION DEVICE P iled March 4, 1.950

Patented Feb. 16, 1954 SN AP-ACTION DEVICE Caton Bradley, Durham,

mesne assignments, to The Conn., assignor, by Sessions Clock Company, a corporation of Connecticut Application March 4, 1950, Serial No. 147,605

10 Claims. l

The present invention relates in general to snap-action devices and in particular to an improved switch-arm for a snap-action switch of the miniature type adapted especially for uses calling for minuteness of movement of the switchactuating means, and a capacity for interrupting relatively-high currents at normal voltage ratings.

An object of the invention is to provide a superior snap-action device.

A further object of the invention is to provide a superior snap-action switch of the miniature type characterized by a relatively-thin and substantially-i'lat casing.

A still further object of the invention is to provide a miniature-type snap-action switch of simple, durable and economical construction and capable of interrupting relatively-high currents.

A still further object of the invention is to provide a miniature-type snap-action switch with a superior switch-arm having structural characteristics such that relatively-small movement of one end of the switch-arm will impart relatively-large movement to the opposite end thereof.

A still further object of the invention is to provide a highly-sensitive snap-action device having a supporting-portion provided with a preset curvature eccentric to the center thereof, whereby minute movement of one end of the snap-action device imparts a disproportionatelylarge movement to the opposite end of the device.

Other objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. l is a plan view of the snap-action switch embodying the novel switch-arm of this invention;

Fig. 2 is a front elevation partly in section of the snap-action switch of Fig. 1 showing the switch-contacts open;

Fig. 3 is a view similar to Fig. 2 but showing the position the parts assume when the switchcontacts are closed;

Fig. 4 is an end elevation in section of the switch on line 4 4 of Fig. 2

Fig. 5 is a plan view of the novel snap-action device or switch-arm used in the snap-action switch;

Fig. 6 is a side elevationvofthe' snap-action device ofFig. 4;` W Wl Fig. 7 is a side elevation in section of a .modiflcation of the snap-action switch in which the contacts of the switch are normally closed and adapted to be opened by actuation of the switcharm;

Fig. 8 is an enlarged plan view of tion of the snap-action device of Fig. 5;

Fig. 9 is an enlarged side elevation o1 the,4

snap-action device of Fig. 8.

The showing of Figs. 1 through 6 tion, the snap-action device is constructed soas to be responsive to a minimum actuating -force and yet have relatively-large movement so as` to incorporate good current interrupting capacity when used in a switch. To these ends, the snapaction device comprises a material indicated generally at I5 which, in effect, is a thin metal leaf spring formed preferably of a phosphorous bronze alloy, although beryllium copper and equivalent metal alloys may be used. This spring-strip I5 is provided with two slots I6 and I1 extending longitudinally of the strip and in laterally-spaced, substantially parallel relationship so as to divide the strip I 5 into three reaches I8, I9, and 20, each reach being joined integrally at its opposite ends to the corresponding ends 2I and 22 respectively of the springstrip I5. The center reach I 9 of the springstrip is,I in the present embodiment, slightly wider than the two side reaches I8 and 20 and is formed at a point substantially intermediate its opposite ends with a fastening-element constituting a vertical substantially rectangular aperture or slot 23.

Referring especially to Fig. 6, it will be seen that the center reach I9 of the spring-strip is provided with a pre-set curvature which is offset from the plane of the spring-strip, the oilset of the curvature of the center reach I9 being downwardly of the plane of the spring-strip. It will be noted, moreover, that the pre-set curvature of the center reach I 9 is not of uniform radius but embodies a section 24 of minimum radius which is eccentric to the center of the spring-strip, that is to say, the section 2479i minimum radius is nearer one endv of the center reach I9- than its opposite end. --This novel-cori-E s'tructionof the spring-strip provides afstiffness a modifica-- thin strip of springv factor which contributes directly to the effectiveness of the snap-action device as the switcharm of a snap-action switch.

It has been discovered that a strip of spring metal constructed in the manner described above and supporting it by fastening-means at the center of its curved reach, will be actuated by depressing that end of the spring-strip which is adjacent the section 24 of the curved center reach, and which is hereinafter referred to as the actuating-end of the spring-strip, that is to say, the opposite end of the spring-strip will bede-V lected downwardly, and will snap back to its original position upon release of the' actuatingend of the spring-strip. of force applied to the actuating-endl of the spring-strip and the consequent movement of the said actuating-end thereof are extremely small. By way of example, the energy required to operate a spring-strip of the proportions illustrated herein is of the order of ifteen-thousandthsr inchounces, and the amount of movement of the actuating-end of the spring-strip is ina range'of from one-thousandthto five-thousandths of an inch, the resulting movement of the opposite end of the spring-strip beingrv substantially ten times that ofv its actuating-end. This characteristic of the spring-action device adapts it particularly to snap-actionswitches ofthe miniature type in that the relatively-large movement of one end of the snap-action device, in response to relatively-minute movement of its opposite actuating-end permits the'use of the snap-'action device as a switch-arm; having capacity'for interrupting relativelyelarge currents at normal voltage ratings.

Figs. l, 2, 3 and 4 illustratev a miniature-type snap-action switch, identified ini general byl the numeral 25, and embodying a switch-arm ofthe type disclosed in Figs. 5x and 6 and hereinabove described. The snap-action switch 25 comprises a composite base-member, indicated generally at 26, and a cover-member 21 within which the switch-arm i5 is supported in vertically-spaced relationship with respect to theY composite basemember, in the manner described below. The composite base-member 25 comprises upper and lower laminae of substantially-identical dimensions and consisting of relatively-thin insulation material, the upper laminaf28 being preferably cardboard or fabricV impregnated withY a suitable plastic material, the lower lamina 29 beingl preferably Bakelite or the equivalent. The opposite ends of the upper and lower laminae are secured together by eyelet-grommets Bt- 30, while the central portion of the upper lamina 28 is provided with an embossed or raised portion 32T substantially equivalent in length tothe length of the cover-member 2l, thereby to provide a clearancespace 'J3 between the underside of the embossment 32 of the upper lamina and the upper side of the lower lamina, for accommodating one of the contact terminals ofthe switch inthe manner hereinafter described.

The upper lamina 28 is provided with a contact 34 formed of a good conducting`l material such as silver or copper, the said contact 34 being located' on the upper face of the upper lamina 23. The contact 34 projects down through the upper lamina 28, and mounts on the lower endv thereof a contact terminal or blade 35, the inner end of which is secured to the contact 34. As so assembled on the base, the blade 35 is accommodated in the clearance-recess 33 between the upper and switch, that is to say,

Moreover, the amount:` w

lower laminae of the base and projects outwardly at substantially right angles thereto.

The cover-member 2T of the switch is formed of metal such as thin sheet brass, and comprises a iat rectangular top 35 and side and end 'walls 31 and 3S respectively bent down at substantially right angles to the top 3E. In the present embodiment, the combined height of the cover and the thickness of the composite base is substantially equal to one-sixth the over-all length of the a switch substantially one and one-half inches long would be approximately one-quarter of an inch thick.. It will be appreciated, however, that these dimensions are not limiting on` the invention, but serve merely to illustrate the-relative proportions thereof and to indicate the-minuteness of the assembled switch.

Formed at the left-hand end of the covermember, as seen in Figs. l and 2, is a vertical aperture 3S which is adapted to accommodate a push button 45, the upper end of which projects up through the aperture in the top of the covermember for manually operating the switch-arm, in the manner hereinafter described. Y

Formed at the center of the top 36 of the covermember is a generally circular indenture `4i having a bottom wall il?. provided with a rectangular' slot 43 in which is secured the lower reduced end 44 of a second contact terminal L35. The latter constitutes a blade-like member which is held from passing down through the slot in the bottom wall of the indenture by engagement of the shoulders of its reduced end with the bottom wall of the indenture. The terminal 45 may project upwardly substantially vertically from the top of the cover, but isvpreferably bent over at substantially right angles to extend outwardly from the side of the switch in the direction of the lower terminal or blade 35.

The reduced end 44 of the blade 45 projects down through the bottom wall 42 of the indenture, and constitutes'fastening-means, both for securing the blade 45 in the indenture of the cover and for securing the switch-arm l5 rigidly to the underside of the bottom wall of the indenture. To these ends, the reduced end 44 of the blade 45 extends through the aforesaid slot 23 in the center reach I9 of the switch-arm l5 and is swaged over on the undersidethercof, as shown especially well in Fig. 2. In this connection, it will be noted that the width of the indenture 4i is no greater than the width of the center reach I9 of the switch-arm, and hence, its side reaches I8 and 2U have clearance for extending on opposite sides respectively of the indenture, as shown in Fig. 4. Moreover, since the center reach I9 is below the plane of the side reaches iS and 20, the latter will be supported in a substantially common horizontal plane slightly above the bottom wall 42 of the indenture.

Thus, with the switch-arm fixedly secured at its center only to the underside of the cover, the opposite ends ofthe switch-arm are free and un supported. The end of the switch-arm which is adjacent the section 24 of minimum radius of the center reach I9 and which corresponds to the lefthand end of the switch-arm,v as seen in Fig. 2, is provided with a vertical aperture 46 arranged to accommodate the reduced end 41 of the aforesaid push button 40, the latter being formed with an annular ange 48 intermediate its opposite ends which seats on the apertured end of the switcharm and serves to hold the push button thereon with its reduced end 4-1 projecting down through the aperture 46 and constituting a stop-finger enacaricia` gageable with thevembossment 3`2, to limit-thedownward deiiection of this end of-the switch-- arm. The annular ange 48 also serves vto engage against the underside of the cover to limit the upward movement of the corresponding end of the spring-arm and also to hold the push button from rising up out of the aperture 39 in the cover. By means of this arrangement the amount of pre-travel and over-travel of the push button can be held to a minimum just sufficient to enable actuation of the switch-arm to be effected.

The opposite or right-hand end of the switcharm is provided on its underside with a contact 49 which is preferably formed of a good vconducting metal such as silver, copper, or the like, and located substantially opposite the contact 34 and secured to the switch-arm by swaging over the. upwardly-projecting end of the rivet-shank on the top side of the switch-arm. The swaged-over. portion of the contact i9 constitutes an abutment adapted to engage the underside of the cover and to limit the upward movement of the corresponding end of the switch-arm. This arrangement also serves to reduce to a minimum the amount of pre-travel of the push button necessary to effect actuation of the switch.

To assemble the cover-member 21 and its attached switch-arm I on the base-member 25, the embossment of the latter is provided with a pair of indentures 5l in opposite edges thereof respectively, arranged to accommodate metal tongues 52 which are formed integrally with and extend down from the bottom edges of the respective sides 31 of the cover-member, the metal tongues 52 being adapted to be turned under beneath the edges of the embossment 32 of the upper lamina 28 of the base-member to secure the cover-member thereto, as shown especially well in Fig. 4.

Operation of the showing of Figs. 1 through 6 inclusive Normally, the push button 40 is supported by the left-hand end of the switch-arm in its uppermost position relative to the cover of the switch, the contact 49 at the opposite end of the switcharm being in vertically-spaced relationship with respect to the contact 34 of the base-member. By reason of the abutment of the upper face of annular flange 48 on push button 4e against the under face of cover member 27, and also because of the abutment of the swaged-over portion of contact 49 against the under surface of the cover, as mentioned previously, a major portion of the pre-travel of the push button necessary before actuation of the switch is effected is eliminated. It will be noted that in this condition, the central reach i9 to which blade 45 is connected is substantially fiat throughout its length except for that portion at one end which is provided with the aforesaid pre-set curvature. Now, when the push button :i9 is pushed down, it travels initially the distance necessary to take up whatever small amount of pre-travel remains before actuation of the switch occurs. Thereafter, further deection of the corresponding end of the switch-arm serves to deflect the opposite end of the switch-arm downwardly to bring its contact 49 in engagement with the contact 34. Due to the pre-set curvature of the center reach I9 of the switch-arm and, in particular, the section 24 of minimum radius thereof, the movement of the contact 49 is relatively large in-.com-g pari-son with the total zriovemer-itsof` the" push button less its pre-travel. `In the particular embodiment kof. the invention shown herein, the actual movement of the contact 49 is oi'4 the order of ten times the total movement of .the push button less its pre-travel and, consequently, due to the relatively-wide spacing of thecontact 49 and the contact 34, the switch is capable of interrupting currents, which for a miniature switch of this type are relatively heavy.

The showing of Fig. 7

The snap-action switch shown in Figs.- 1 through 6 inclusive is of the type wherein the contacts are normally open and are closed by depressing and releasing the push button of the switch. It will be appreciated, however, that the switch may be modied so that normally the switch will maintain a circuit closed and will open the circuit by depressing the push button. To this end, the contact 34 is shown mounted in the cover-member of the switch and insulated therefrom by an insulating grommet 5D, the contact 49 in the corresponding end of the switcharm I5 being mounted on the upper face thereof so that, it is adapted normally to engage the Thus, normally, engagement of the contact `-49 with the contact 34 will maintain a circuit closed, the circuit being opened whenever the push button 40 is depressed.

, The showing of Figs. 8 and 9 Figs. 8 and 9 show a modification of a snapaction device for use with a switch. In its modied form, the snap-action device |5a comprises a thin strip of spring metal similar inform and materialto the snap-action device` I5 hereinabove described and illustrated in Figs. 1 through 6, the modified snap-action device |5a differing therefrom in the structure and function of the side reaches and central reach of the springstrip. Thus, in the spring-strip |5a, the slots IBa and Ha which extend longitudinally thereof in straight substantially-parallel relationship, divide the spring-strip into side reaches |8a and 25a and a center reach l9a. The latter is substantially flat and imperforate, whereas the side reaches lila and 20a respectively are formed with pre-set curvatures oifset below the plane of the center reach |911 and having sections 24a and 24h respectively of minimum radius eccentric to the centers of the side reaches. In this connection, the. centers of the side reaches are provided with substantially rectangular slots 23a and 23h respectively which serve as fasteningelements for securing the spring-strip to the underside of the cover of a snap-switch in the manner hereinafter described.

The modied switch-arm I5a will be assembled in the cover-member of the switch in the manner hereinabove described for the switch-arm l5 except that the switch-arm |5a will be xedly secured to the underside of the cover-member by a pair of fastening-means' engaged in the aforesaid slots 230iY and 23h of the switch-arm, the action of the assembled switch-arm 15a being. substantially identical to the actionfof the snapswitch hereinabove described.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristicsof the invention, and the present embodiments are. therefore, to; be considered in all respectsaslillustrative and not-restrictive, and al1 changes coming.within` the. meaning. and ...equiv-l alencylrange' ofthe appendedclaims are intended to be embraced therein.

` I claim:

1 "A 'snap-action device comprisinga strip of spring material slottedl longitudinallyI to -form a plurality of laterally-spacedreaches ljoined integrallyat their opposite ends to-the corresponding ends of the strip, one of said reaches being substantially flat throughout a major portion or" its length and having a single pre-set curvature offset 'from the plane/of 'said strip and eccentric to a point substantially intermediate the opposite ends thereof; -andn'iounting means 'to which said strip is secured 'at a point substantially intermediate its opposite ends to cause said 'ends to project outwardlyvin opposite directions 'in unsupported condition from such point, whereby snap-action movement of 'one of said unsupported 'ends is effected in a direction substantially perpendicular to the Vplane of said strip by the applicationv of a force at the opposite unsupported end of said strip in 'the' direction of said oiset and substantially perpendicular to the plane'of said strip.

2. A switch-arm construction for a snap-action switch comprising: 'a Ystrip of spring material slotted longitudinally to form a plurality of laterally-spaced reaches joined integrally at their opposite ends to the corresponding ends of the strip and extending continuously therebetween, one of said reaches being substantially flat throughout a major portion oi its length and having a single pre-set curvature oiset from the plane of said strip and longitudinally from the center of said reach; mounting-means to which said strip is secured at a point substantially intermediateits opposite endsto cause said ends to project outwardly in opposite directions in unsupported condition from such point; and a contact carried by one of saidunsupported ends for snap-action movement in a direction substantially perpendicular to the plane of said strip by the application of a force at the opposite end of said strip in the direction of said offset and substantially perpendicular to the plane of said strip.

3. A switch-arm construction for a snap-action switch as dened in claim 2, wherein said strip of spring material is slotted to provide an inner central reach and a pair of outer reaches, said inner central reach having said pre-set curvature, said strip being supported solely by attachment of said central reach to said mounting means.

4. A switch-arm construction for a snap-action switch as defined in tral reach is provided with an aperture and said mounting means is provided with a lug which engages in said aperture for securing said strip to said mounting means.

5. A switch-arm for a snap-action switch havingtwo contacts and contact terminals therefor, said switch-arm comprising: a strip of spring material slotted longitudinally to form a plurality of laterally-spaced reaches joined integrally at their opposite ends to the' corresponding ends of the strip and extending continuously therebetween, one of said reaches being substantially flat throughout a major portion of its length and having fastening-means substantially intermediate its opposite ends for connecting said strip to one of said contact terminals with the opposite ends of said strip unsupported, and a pre-set curvature in saidone reach, said pre-set curvature 'beingoffset 'from the plane of said strip and having al section of minimum radius claim 3, wherein said ceneccentric to the center of said one reach; one of said contacts being secured to that end of saidA strip which is farthest from the said section of minimum radius of the curved reach, said contact'being arranged to be moved relative to the second contact of said switch by relatively minute movement of that end of said strip which isadjacentv the section of minimum radius of said curvedfreach.

6. A snap-action switch comprising a basemember having a contactand contact terminal therefor; a cover-member on said base-member; a second contact andl contact terminal, said second contact terminal being mounted on said cover-member; a switch-arm adapted to be supported within said cover-member above said base-member, said switch-arm comprising a strip of spring material slotted longitudinally to form a plurality `of laterally-spaced reaches joined integrally at vtheir opposite ends to the corresponding ends vof the strip and extending continuously therebetween, one of said reaches being substantially'at throughout a major portion of its length and having fastening-means substantially intermediate its opposite ends arranged to connect said strip to the terminal in `said cover-member thereby to support said stripV with its opposite ends free, and a pre-set curvature in said one reach offset from the plane of said strip and from the center of said one reach; said second contact being secured to one free end of said strip substantially opposite the contact in the base-member of said switch, said second contact being arranged to be snapped into and from engagement with the contact in said base-member by actuation of the opposite free end of said strip; and actuating-means mounted in said cover arranged to engage the aforesaid opposite free end of said strip for actuating the latter.

7. A snap-action switch comprising a basemember having a contact and contact terminal therefor; a cover-member on said base-member; a second contact and contact terminal, said second contact terminal being mounted on said cover-member; a switch-arm adapted to be supported within said cover-member above said base-member, said switch-arm comprising a strip of spring material slotted longitudinally to form -two side reaches and a center reach, said reaches being joined integrally at their opposite ends to the corresponding ends of the strip and extending continuously therebetween, said center reach being substantially nat throughout a major portion of its length and having fastening-means substantially intermediate its opposite ends arranged to connect said strip to the terminal of said cover-member thereby to support said strip with its opposite ends free, and a pre-set curvature in said center reach offset from the plane of said strip and from the center of said center reach; said second contact being secured to one free end of said strip substantially opposite the Contact in the base-member of said switch, said second contact being arranged to be snapped into and from engagement with the contact in said base-member by actuation of the opposite free end of said strip; and actuatingmeans mounted in said cover arranged to engage the aforesaid opposite free end of said strip for actuating the latter.

8. A snap-action switch comprising a basemember having a contact and contact terminal therefor a cover-member on said base-member; a second contact and contact terminal, said second contact terminal being mounted on said cover-member; a switch-arm adapted to be supported within said cover-member above said basemember, said switch-arm comprising a strip of spring material slotted longitudinally to form two side reaches and a center reach, said reaches being joined integrally at their opposite ends to the corresponding ends of the strip and extending continuously therebetween, said center reach being substantially flat throughout a major portion of its length and having fastening-means substantially intermediate its opposite ends arranged to connect said strip to the terminal of said cover-member thereby to support said strip with its opposite ends free, and a pre-set curvature in said center reach offset from the plane of said strip, said pre-set curvature having a section of minimum radius eccentric to the center of said strip; said second contact being secured to one free end of said strip substantially opposite the contact in the base-member of said switch, said second contact being arranged to be snapped into and from engagement with the contact in said base-member by actuation of the opposite free end of said strip; and actuating-means mounted in said cover arranged to engage the aforesaid opposite free end of said strip for actuating the latter.

9. A snap-action switch comprising a basemember having a contact and contact terminal therefor; a cover-member on said base-member; a second contact and contact terminal, said second contact terminal being mounted on said cover-member; a switch-arm adapted to be supported within said cover-member above said basemember, said switch-arm comprising a strip of spring material slotted longitudinally to form two side reaches and a center reach, said reaches being joined integrally at their opposite ends to the corresponding ends of the strip and extending continuously therebetween, said center reach being substantially at throughout a major portion of its length and having an aperture substantially intermediate its opposite ends; fastening-means arranged to engage in the said aper ture of said center reach to connect said strip to the terminal of said cover-member thereby to support said strip with its opposite ends free, and a pre-set curvature in said center reach olset from the plane of said strip, said pre-set curvature having a section of minimum radius eccentric to the center of said strip; said second contact being secured to one free end of said strip substantially opposite the contact in the basemember of said switch, said second contact being arranged to be snapped into and from engagement with the contact in said base-member by actuation of the opposite free end of said strip; and a push button supported on the aforesaid opposite free end of said strip and arranged to project through said cover for actuating said strip.

10. A snap-action switch comprising verticallyspaced supporting members; a contact and contact terminal associated with each of said supporting members; a switch-arm adapted to be supported by one of said supporting members in vertically-spaced relationship to the other of said supporting members, said switch-arm comprising a strip of spring metal slotted longitudinally to form a plurality of laterally-spaced reaches joined intergrally at their opposite ends to the corresponding ends of the strip and extending continuously therebetween, one of said reaches being substantially at throughout the major portion of its length and having fastening means substantially intermediate its opposite ends arranged to connect said strip to the terminal of its respective supporting member thereby to support said strip with its opposite ends free, and a pre-set curvature in said one reach offset from the plane of said strip and from the center of said one reach; one of said contacts being secured to one free end of said strip substantially opposite the contact of the said other supporting member of said switch, said contact on said strip being arranged to be snapped into and from engagement with the contact of the said other supporting member by actuation of the opposite free end of said strip; and actuating means mounted in the said one supporting member arranged to engage the aforesaid opposite free end of said strip for actuating the latter.

CATON BRADLEY.

References Cited in the le 0f this patent UNITED STATES PATENTS 

